Electrolytic bath for use in electrodeposition of ferromagnetic compositions



United States Patent Office 3,032,485 Patented May 1, 1962 3,032,485ELECTROLYTIQ BATH FOR USE IN ELEC- TRODEPGSITIGN F FERROMAGNETECCOMPOSlTl0N Ignatius Tsu, Jerome S. Sallo, and Robert D. Fisher, Dayton,Ohio, and Harsnkh J. Modi, West Lafayette, Ind., assignors to TheNational Cash Register Company, Dayton, Ohio, a corporation of MarylandNo Drawing. Filed Oct. 1, 1958, Ser. No. 764,522 25 Claims. (Cl. 204-43)This invention relates generally to the manufacture of ferromagneticmemory elements such as wires, bobbin and torroidal shaped cores, andthe like, for use in present day electronic computers and dataprocessors, and more specifically relates to new and improvedelectrolytic baths for use in the manufacturing of such elements whichpossess greatly improved magnetic characteristics than heretoforepossible.

In most electronic computer and data processor applications, it isgenerally highly desirable that the magnetic memory elements berelatively small in size, require negligible expenditure of time andeffort in order to be electrically connected in circuit, be physicallysturdy and economical to manufacture utilizing mass productiontechniques, possess relatively high magnetic remanence and relativelylow magnetic coercivity properties, be readily adaptable to fastswitching operations measured in fractions of microseconds, andadditionally, possess substantially rectangular hysteresischaracteristics resulting in substantially high signal-to-noise ratios.

Various attempts have heretofore been made to produce such magneticmemory elements for information storage purposes by electroplating anelectrically conductive carrier with a relatively thin coating of analloy having magnetic properties. Even though present day electroplatingtechniques possess practically unlimited potentialities in themanufacture of such elements, to date however, to the knowledge ofapplicants there is yet to be produced thereby any memory element whichpossesses all of the above-mentioned characteristics.

Consequently, the primary object of the present invention is to devise anew and improved aqueous electrolytic bath for utilization in theprocess of electrodeposition of a ferromagnetic coating onto anelectrically conductive carrier whereby magnetic memory elements areproduced which possess all of the above-mentioned characteristics.

Briefly, in accordance with the present invention, such a bath includesas essential constituents iron ions in a concentration in the range of.7 to 16 grams per liter, nickel ions in a concentration in the range of3 to grams per liter, molybdenum (VI) in a concentration in the range of.1 to 1 gram per liter, and a complexing agent.

More specifically, the plating bath preferably contains simple salts ofiron, nickel, and molybdenum in complexed form wherein iron is initiallyadded as either a ferrous salt such as ferrous chloride (FeCl -4H O) oras a ferric salt such as ferric chloride (FeCl -6H O). From thestandpoint of economic availability, the chlorides of iron arepreferred, however, any salt of iron may be used provided the anion doesnot cause precipitation in the overall system.

Nickel is preferably added to the plating bath as a simple nickelchloride salt (NiCl -6H O). However, following the addition, severalnickel species may appear as free nickel ions, nickel amine complexes,nickel chelates, nickel addition agent complexes, and nickel complexeswith other added metal salts. Nickel may be added in the form of othersalts, as an illustrative example nickel sulfate (NiSO -6H O) providedprecipitation does not occur. The form in which nickel exists in a givensystem depends upon many factors such as the nickel concentration, pH,ammonium ion concentration, chelating agent concentration, ironconcentration, addition agent concentration, complexing agentconcentration, temperature, and concentration of other metal salts. Itis by varying these factors that a wide range of magnetic properties isobtained. In addition, the nickel species in the bulk of the solutionare not necessarily the same as the nickel species occurring in theso-called double layer at the cathode. It is the latter species fromwhich deposition actually occurs and which is of major importance indetermining the magnetic properties of the deposit.

Molybdenum ing bath and it is preferably added to the bath in the formof sodium molybdate (Na MoO -2H O). However, molybdenum may be added inthe form of other compounds provided they cause no precipitation in theoverall system. For example, molybdenum may be added in the form ofmolybdic acid (H2MOO4), phosphomolybdic acid (P O 24MoO -XH O),potassium molybdate ammonium molybdate [(NH MoO -2H O], ammoniumheptamolybdate [(NH4)6M0I1O24'4H2O], molybdenum trioxide (M00 etc.However, the concentration of molybdenum (V1) is critical and theoptimum concentration depends upon the overall conditionof the system.In fact, in the preferred bath if the molybdate concentration isexcessive, for example an ionic concentration thereof in excess ofapproximately 2 grams per litter, little or no deposit results.Molybdate in such bath has been found to effect the plating bathsimilarly to addition agents in that, for example, molybdate lowers thedischarge potential of the plating process and is believed to lcjo$plexwith the iron and/ or nickel constituents in the Due to the fact thateven the hydroxides of iron begin to precipitate even in acid solutions,it is desirable to utilize a complexing agent to maintain the platingbath in solution. The preferred complexing agent for this purpose isammonium citrate [(NH HC H O However, any material which forms a complexwith the iron ions of sufiicient solubility and stability is a suitablecomplexing agent. For example, complexing agents which may be used withequal success are sodium citrate and potassium citrate (K C H5Oq2H2O).Various acids such as citric acid (H3C6H507'XH2O), glycolic acid (C H O-XH O), aspartic acid (C H O N-XH O), and the sodium salt ofethylenediaminetetraacetic acid etc. may be used, provided there is nobreakdown of the complex for example anodic oxidation during the platingprocess which might form oxidation. products at the anode thus modifyingthe plating bath and, consequently, modifying the magnetic properties ofthe cathode deposit.

In the present invention, it is believed that the essential function ofthe complexing agent is to provide a (VI) has an appreciable effect inthe platsoluble reservoir of iron, nickel, and/or molybdenum (VI) ionsfrom which are formed, through dynamic equilibria, the species fromwhich the deposition actually occurs. The complexing agent must be of aconcentration in the bath to supply the iron, nickel and molybdenum (VI)species rapidly enough through equilibria to provide a suitableconcentration of species for deposition, and yet, not rapidly enough toform an appreciable amount of other species whose solubility limits areexceeded to cause precipitation in the bath. Since the complexing agentpartially determines the concentration of the reactive species presentin the plating bath, the choice of the particular complexing agent hasan effect on the composition and structure, and consequently themagnetic properties of the cathode deposit, which influence may bemodified by the other constituents of the plating system. In thepreferred ferrous plating bath, it is desirable that a minimum molarratio of l to 1 be maintained between the relative citrate and ferrousion concentrations.

Ammonia is preferably added to the plating bath in the form of ammoniumhydroxide (NH OH) to control the pH thereof. Even though it is possibleto utilize the plating baths, in accordance with the present invention,to prepare cathode deposits having magnetic properties without theaddition of ammonia, it is desirable that the baths have a pH within therange of 7.5 to 9.5, preferably 8.5. Ammonia, aside from controlling thepH, is believed to modify the bath through complex formations and to bepart of the reservoir complexes from which deposition occurs. Amineshave been found to be less suitable than ammonia for controlling thebath pH, however, non-complexing bases such as sodium hydroxide (NaOI-I)and potassium hydroxide (KOH) may be used with equal success, providedthe amounts added to the citrate baths are of insuflicient quantity tocause precipitation therein. As the plating bath is operated within atemperature range of 80 C. to 95 0., preferably 90 C., the ammoniaconcentration is depleted due to evaporation and, consequently, it isnecessary to continuously replenish the bath with ammonium hydroxide tomaintain the pH thereof at the preferred 8.5 value.

Ammonium is preferably added to the plating bath in the form of ammoniumchloride (NH Cl). As the ammonium ions exert a common ion effect on theammonia complexes, they are believed to influence the concentration ofthe ionic species present in the system and thereby effect the structureand magnetic properties of the electrodeposit. Other ammonium salts i.e.ammonium sulfate [(NH SO may be used with equal success providedprecipitation does not occur in the bath as a result of the addition.

Shown below in charts I and II, are two forms of new and improvedaqueous electrolytic baths having preferred constituent concentrationsin accordance with the teachings of the present invention, for use inthe process of deposition of an iron-nickel-molybdenum coating on anelectrically conductive carrier, in which process the carrier issubjected as a cathode to electrolytic action in the bath, during whichthe coating formed thereon possesses greatly improved magneticcharacteristics. It is to be noted that in the upper half of each chart,is given the concentration of each compound in the actual bath measuredin grams per liter of aqueous solution; in the lower half of each chart,is the concentration given in grams per liter of aqueous solution ofeach constituent present in solution as contributed by each compound. Ineach instance, the minimum, optimum, and maximum concentrations for eachconstituent is given in tabular form. It is to be understood of coursethat the upper and lower concentration limits of each compound andconstituent of the bath are not critical in that they specificallydefine limits above and below which is a definite zone of demarcation ofall useful magnetic properties possessed by the cathode deposit.

Plating Bath Compounds Mini- Opti- Maximum mum mum Ferrous Chloride(FeCl2-4H2O) 45 50 55 Nickel Chloride (NlCl2-6H2O) 10 20 40 SodiumMolybdate ENazMoOr-ZHzO) .5 1 3 Ammonium Citrate (N H4) 2HC6H5O7]Ammonium Chloride (N HiCl) 35 50 100 Plating Bath Constituents Mini-Opti- Maximum mum mum Ferrous Ion Concentration 12 14 16 Nickel IonConcentration- 3 5 10 Molybdenum (VI) Concentr 1 .4 1 Citrate IonConcentration 88 104 113 Ammonium Ion Concentration 12 17 34 PlatingBath Compounds Mini- Opti- Maximum mum mum Ferric Chloride(Ft-101361120) 4 6 15 Nickel Chloride (NiClz-fiHzO) 10 20 40 SodiumMolybdate iNazMoOi-2Hz0) .5 1 3 Ammonium Citrate (N HO2HCGHEO1] 4O 50125 Ammonium Chloride (N H401) 25 5O 75 Plating Bath Constituents Mini-Opti- Maximum mum mum Ferric Ion Concentration 7 1 3 Nickel IonConcentration 3 5 10 Molybdenum (VI) Concentration 1 .4 1 Citrate IonConcentration 33 42 104 Ammonium Ion Concentration-.- 8 17 25 Eventhough the new and improved aqueous electrolytic baths, just described,find utility in any of the numerous present day electroplating process,a preferred process will be described utilizing the baths of the presentinvention whereby magnetic data storage devices of the twistor type,such as that shown and described in copending application Serial No.696,987, by J. R. Anderson, et al., filed November 18, 1957, andassigned to the present assignee, are fabricated and exhibit improvedmagnetic characteristics than heretofore possible.

After the electrolytic bath has been prepared, either I or II, and thepH adjusted to a value in the range of 7.5 to 9.5, preferably 8.5, thetemperature is then adjusted to a value in the range of 80 C. to 95 C.,preferably 90 C., even though the bath may successfully be operated atordinary room temperature. The bath is then introduced into aconventional rubber-lined steel plating tank, or an equivalent inertcontainer. The carrier, onto which the deposit is to be formed, may beof any of a variety of non-magnetic electrically conductive materialssuch as alloys of copper, aluminum, brass, bronze, etc. In fact thecarrier may even be of such materials as glass, plastic, or ceramic,assuming of course that it has previously been provided with a suitableelectrically conductive skin covering in a well-known manner. However,in the fabrication of the twistor types of bistable magnetic datastorage devices, as disclosed in the aforementioned copendingapplication, it is preferred that the carrier be a Phosphor-bronze wirehaving a diameter of approximately 9 mils. It is, of course, necessarythat the metallic carrier be cleaned before plating through the use ofthe conventional alkaline-acidwater methods which are well known in theplating industry.

In the twistor type of device it is desirable to secure a relativelythin deposit on the carrier in the order of one ten-thousandth of aninch so as to maintain eddy current losses therein at a minimum duringoperation of the device, and yet be thick enough to insure adequateoutput and not fracture when torsional stresses are applied thereto asdescribed in the copending application. Consequently, it is desirablethat the carrier be exposed as a cathode in the bath for only a shortperiod of time, i.e. from approximately 30 seconds to 3 minutes,preferably in the order of 2 minutes depending upon, of course, thecathode current density to be used in the plating process. To accomplishthis, the process is made a continuous one whereby the carrier is movedthrough the bath at a constant speed, by any well known means, withelectrical contact at all times maintained with the carrier to supplycurrent thereto. The carrier is preferably centrally encompassed at alltimes while in the bath by a helicalshaped anode having a coil diameterof approximately one inch and composed of an electrically conductivewire of approximately 50 mils in diameter.

The choice of anode material may not arbitrarily be made, however,iron-nickel, and iron-nickel-molybdenum may successfully be usedprovided the anode is bagged in a conventional manner to prevent sludgeformations at the anode from entering the bath solution. One of theimportant factors associated with the choice of anode material isoxidation in the system. When using bath I, ferrous ions are convertedto ferric ions due to oxidation of the bath and high concentration offerric ions therein is to be avoided. Inert anodes such as platinum, orthe like, may be used provided they do not lead to excessive oxidationof the system. It has been found that in each of baths I and II,molybdenum anodes are preferred as they do not have to be bagged andtend to replenish the bath with molybdenum. However, even when amolybdenum anode is used, it is necessary to continually add molybdatesolution to the bath in order to maintain the molybdate concentrationconstant at the desired value. Additionally, it is necessary that nickeland iron solutions be continually added to the bath to also maintain theconcentrations thereof constant at their respective values during theplating process.

The current density involved in the deposition process is not criticaland may range, for example, from 150 to 500, preferably 250, amperes persquare foot of carrier surface area exposed in bath I and from 200 to1000, preferably 250, amperes per square foot of carrier surface areaexposed in bath II. The current density primarily determines the rate ofdeposition of the metallic ions onto the cathode. This affects the rateof diffusion into the cathode film which influences the amount ofdepositing species which must be in equilibrium with the reservoircomplexes. Consequently, the bath and current density must be compatibleand the current density cannot arbitrarily be chosen. For example, anyaddition agents in the system are less effective at relatively highcurrent densities and, consequently, larger quantities must be used. Asthe current density is one of the prime factors which determine thestructure of the deposit, it is generally necessary to modify theplating system to permit the use of a specific current density.

On emergence from the plating bath, the ferromagnetic element is rinsedand dried and is then ready to be operated as a coincident currenttwistor type of data storage device in the following manner as fullydescribed in the aforementioned copending application:

The core, along with the ferromagnetic coating, is simultaneouslystretched and twisted and the ends thereof are thereafter held in afixed position. As a result of the stretching and twisting, the easydirection of magnetization of the coating is oriented from a directionsubstantially parallel to the longitudinal axis of the core to one ofsubstantially helical configuration about the body of the core andthroughout its length as the threads of a screw. Such a ferromagneticcoating has been found to possess a substantially high positive andnegative magnetic remanence and substantially rectangular hysteresischaracteristic. Consequently, selected length portions of the coating,in the direction of twist, are allowed to attain one or other of the twostable states, namely, a residual positive or negative remanentinduction. A magnetic field along the direction of twist of :H oerstedsswitches the length portions from one state to another, whereas a fieldof '-H/ 2 oersteds produces only negligible changes in the remanentinduction. A plurality of similar coils, of say 20 turns each, areseparately wound about the coated wire and are positioned in a spacedside-by-side relationship with respect to one another to define acorresponding plurality of helical-path length portions of ferromagneticmaterial. Storage of binary information in a select length portion ofcoating is accomplished by sending a current impulse equal in magnitudeto (1 into the conductive wire of the common core and simultaneouslysending a current impulse equal in magnitude to (1;) into the selectcoil in such directions that the vector summation of the magnetic fieldproduced by the two coincident currents are equal in magnitude to 1-Hoersteds and is oriented in the same direction as the twist or easydirection of magnetization of the coating.

During reading of the selected length portion of the coating, the coreis preferably pulsed to individually develop a magnetic field of :Hoersteds in the opposite direction from the magnetic field developedduring storage of the function. In response to the read impulse, anelectrical signal is or is not available between the ends of thecorresponding coil according to whether the binary information 1 or 0,respectively, has been established in the particular length section ofthe coating as represented by its remanent state.

Listed below in chart form are the electrical operationalcharacteristics of two twistor data storage elements fabricated by thepreviously described plating process which utilize each of the uniqueferrous and ferric baths previously described and differ only in wiresize of carrier.

Ferrous Ferric Bath Bath Degrees of twist/inch of storage elementlength. 145 l0. Approx. one-half coincident current in core for storageof binary data 200 1%.... 75 ma. Approx. one-half coincident current incoil for storage of binary data 100 ma 50 ma. Full coincident current incoil for reading of stored binary data W 500 rna. 500 ma. Voltage outputacross ends of core during reading of binary 1 data- 70 my-.. 75 mv.Signal to noise ratio. 5 Minimum switching ti e- Less than Less than 0.3micro 0.3 micro sec. sec. Diameter of carrier Approx. Approx.

9 mils. 9 mils.

Ferrous Ferric Bath Bath Degrees of twist/inch of storage element length360 10 Approx. one-half coincident current in core for storage of binarydata ma... 60 Approx. one-half coincident current in coil for storage ofbinary data ma. 55 40 Full coincident current in coil for reading ofstored binary data ma.. 300 300 Voltage output across ends of coreduring reading of binary 1 data m 70 7 Signal to noise ratio 5 75Minimum switching time fil sec..- 3 3 Diameter of carrier mils 3 3 Ineach of the storage elements, the coercivity is less than 2 oersteds andthe squareness of the hysteresis loop approximately .99. Consequently,it can thus be seen that by the use of the unique aqueous electrolyticbaths, in accordance with the present invention, new and improvedferromagnetic data storage elements are fabricated by electroplating aferromagnetic coating onto an electrically conductive carrier. Suchelements, in addition to possessing greatly improved magneticcharacteristics than heretofore possible, are readily adaptable to befabricated by mass production techniques thereby maintaining the costthereof at a minimum, and are ideally suited for incorporation inpresent day electronic data processors and computers.

While particular embodiments of the invention have been shown anddescribed, it will be obvious to those skilled in the art ofelectrodeposition of ferromagnetic materials, that changes andmodifications may be made Without departing from the invention in itsbroader aspects, and therefore, the aim in the appended claims is tocover all such changes and modifications as fall within the true spiritand scope of the invention.

What is claimed is:

1. An aqueous electrolytic bath for use in the process of deposition ofa ferromagnetic coating on an electrically conductive carrier in whichprocess said carrier is subjected as a cathode to electrolytic action insaid bath, said bath having a pH in the range of 7.5 to 9.5 andincluding as essential constituents ferrous ions in a concentration inthe range of 12 to 16 grams per liter, nickel ions in a concentration inthe range of 3 to 10 grams per liter, molybdenum (VI) in a concentrationin the range of .1 to 1 gram per liter, and a complexing agent capableof forming soluble ferrous, nickel, and molybdenum (VI) complexes andbeing of sutficient concentration to prevent precipitation of ferrous,nickel, and molybdenum (VI) ions.

2. An aqueous electrolytic bath for use in the process of deposition ofa ferromagnetic coating on an electrically conductive carrier in whichprocess said carrier is subjected as a cathode to electrolytic action insaid bath, said bath having a pH of approximately 8.5 and including asessential constituents ferrous ions in a concentration approximately 14grams per liter, nickel ions in a concentration approximately grams perliter, molybdenum (VI) in a concentration approximately .4 gram perliter, and a complexing agent capable of forming soluble ferrous,nickel, and molybdenum (VI) complexes and being of sufiicientconcentration to prevent precipitation of ferrous, nickel, andmolybdenum ions.

3. An aqueous electrolytic bath for use in the process of deposition ofa ferromagnetic coating on an electrically conductive carrier in whichprocess said carrier is subjected as a cathode to electrolytic action insaid bath, said bath containing ferrous chloride, nickel chloride, andsodium molybdate and including as essential constituents ferrous ions ina concentration approximately 14 grams per liter, nickel ions in aconcentration approximately 5 grams per liter, molybdate ions in aconcentration approximately .7 gram per liter, and a complexing agentcapable of forming soluble ferrous, nickel, and molybdate complexes andbeing of sufiicient concentration to prevent precipitation of saidferrous, nickel, and molybdate ions, said bath having a pH ofapproximately 8.5.

4. An aqueous electrolytic bath for use in the process of deposition ofa ferromagnetic coating on an electrically conductive carrier in whichprocess said carrier is subjected as a cathode to electrolytic action insaid bath, said bath containing ferrous chloride, nickel chloride, andsodium molybdate and including as essential constituents ferrous ions ina concentration approximately 14 grams per liter, nickel ions in aconcentration approximately 5 grams per liter, molybdate ions in aconcentration approximately .7 gram per liter, and a complexing agentconsisting of citrate ions in a concentration approximately 104 gramsper liter, said bath having a pH of approximately 8.5.

5. An aqueous electrolytic bath for use in the process of deposition ofa ferromagnetic coating on an electrically conductive carrier in whichprocess said carrier is subjected as a cathode to electrolytic action insaid bath, said bath containing ferrous chloride, nickel chloride, andsodium molybdate and including as essential constituents ferrous ions ina concentration approximately 14 grams per liter, nickel ions in aconcentration approximately 5 grams per liter, molybdate ions in aconcentration approximately .7 gram per liter, ammonium ions in aconcentration approximately 17 grams per liter, and a complexing agentconsisting of citrate ions in a concentration approximately 104 gramsper liter, said bath having a pH of approximately 8.5 by the addition ofammonium hydroxide.

6. An aqueous electrolytic bath for use in the process of deposition ofa ferromagnetic coating on an electrically conductive carrier in whichprocess said carrier is subjected as a cathode to electrolytic action insaid bath, said bath having a pH in the range of 7.5 to 9.5 andincluding as essential constituents ferric ions in a concentration inthe range of .7 to 3 grams per liter, nickel ions in a concentration inthe range of 3 to 10 grams per liter, molybdenum (VI) in a concentrationin the range of .1 to 1 gram per liter and a complexing agent capable offorming soluble ferric, nickel, and molybdenum (VI) complexes and beingof sufiicient concentration to prevent precipitation of ferric, nickel,and. molybdenum (VI) Ions.

7. An aqueous electrolytic bath for use in the process of deposition ofa ferromagnetic coating on an electrically conductive carrier in whichprocess said carrier is subjected as a cathode to electrolytic action insaid bath, said bath having a pH of approximately 8.5 and including asessential constituents ferric ions in a concentration approximately 1gram per liter, nickel ions in a concentration approximately 5 grams perliter, molybdenum (VI) in a concentration approximately .4 gram perliter, and a complexing agent capable of forming soluble ferric, nickel,and molybdenum (VI) complexes and being of sufilcient concentration toprevent precipitation of ferric, nickel, and molybdenum ions.

8. An aqueous electrolytic bath for use in the process of deposition ofa ferromagnetic coating on an electrically conductive carrier in whichprocess said carrier is subjected as a cathode to electrolytic action insaid bath, said bath containing ferric chloride, nickel chloride, andsodium molybdate and including as essential constituents ferric ions ina concentration approximately 1 gram per liter, nickel ions in aconcentration approximately 5 grams per liter, molybdate ions in aconcentration approximately .7 gram per liter, and a complexing agentcapable of forming soluble ferric, nickel, and molybdate complexes andbeing of sufficient concentration to prevent precipitation of saidferric, nickel, and molybdate ions, said bath having a pH ofapproximately 8.5.

9. An aqueous electrolytic bath for use in the process of deposition ofa ferromagnetic coating on an electrically conductive carrier in whichprocess said carrier is subjected as a cathode to electrolytic action insaid bath, said bath containing ferric chloride, nickel chloride, andsodium molybdate and including as essential constituents ferric ions ina concentration approximately 1 gram per liter, nickel ions in aconcentration approximately 5 grams per liter, molybdate ions in aconcentration approximately .7 gram per liter, and a complexing agentconsisting of citrate ions in a concentration approximately 42 grams perliter, said bath having a pH of approximately 8.5.

10. An aqueous electrolytic bath for use in the process of deposition ofa ferromagnetic coating on an electrically conductive carrier in whichprocess said carrier is subjected as a cathode to electrolytic action insaid bath, said bath containing ferric chloride, nickel chloride, andsodium molybdate and including as essential constituents ferric ions ina concentration approximately 1 gram per liter, nickel ions in aconcentration approximately 5 grams per liter, molybdate ions in aconcentration approximately .7 gram per liter, ammonium ions in aconcentration approximately 17 grams per liter, and a complexing agentconsisting of citrate ions in a concentration approximately 42 grams perliter, said bath having a pH .of approximately 8.5 by the addition ofammonium hydroxide.

11. A process for fabricating magnetic computing devices comprising thesteps of: providing an aqueous electrolytic bath having a pH in therange of 7.5 to 9.5 and including as essential constituents iron ions ina concentration in the range of .7 to 16 grams per liter, nickel ions ina concentration in the range of 3 to grams per liter, molybdenum (VI) ina concentration in the range of .1 to 1 gram per liter, and a complexingagent capable of forming soluble iron, nickel, and molybdenum complexesand being of sufficient concentration to prevent precipitation of iron,nickel, and molybdenum ions; subjecting an elongated electricallyconductive carrier as a cathode to electrolytic action in said bath fora time sufficient to effect the deposition thereon of a ferromagneticcoating which has the property of providing a particularly oriented easydirection of magnetization when stressed; and applying a torsionalstress to said coating, relative to a longitudinal axis of said carrier,by an amount sufficient to establish in said coating an easy di' rectionof magnetization which is oriented at an angle with respect to saidlongitudinal axis.

12. A process for fabricating magnetic computing devices comprising thesteps of: providing an aqueous electrolytic bath having a pH in therange of 7.5 to 9.5 and including as essential constituents ferrous ionsin a concentration in the range of 12 to 16 grams per liter, nickel ionsin a concentration in the range of 3 to 10 grams per liter, molybdenum(VI) in a concentration in the range of .1 to 1 gram per liter, and acomplexing agent capable of forming soluble ferrous, nickel, andmolybdenum (VI) complexes and being of sufficient concentration toprevent precipitation of ferrous, nickel, and molybdenum (VI) ions;subjecting an elongated electrically conductive carrier as a cathode toelectrolytic action in said bath for a time sufficient to effect thedeposition thereon of a ferromagnetic coating which has the property ofproviding a particularly oriented easy direction of magnetization whenstressed; and applying a torsional stress to said coating, relative to alongitudinal axis of said carrier, by an amount suificient to establishin said coating an easy direction of magnetization which is oriented atan angle with respect to said longitudinal axis.

13. A process for fabricating magnetic computing devices comprising thesteps of: providing an aqueous electrolytic bath having a pH in therange of 7.5 to 9.5 and including as essential constituents ferrous ionsin a concentration in the range of 12 to 16 grams per liter, nickel ionsin a concentration in the range of 3 to 10 grams per liter, molybdenum(VI) in a concentration in the range of .1 to 1 gram per liter, and acomplexing agent consisting of citrate ions in a concentration of 88 to113 grams per liter; subjecting an elongated electrically conductivecarrier as a cathode to electrolytic action in said bath for a timesufficient to effect the deposition thereon of a ferromagnetic coatingwhich has the property of providing a particularly oriented easydirection of magnetization when stressed; and applying a torsionalstress to said coating, relative to a longitudinal axis of said carrier,by an amount sufficient to establish in said coating an easy directionof magnetization which is oriented at an angle with respect to saidlongitudinal axis.

14. A process for fabricating magnetic computing devices comprising thesteps of: providing an aqueous electrolytic bath having a pH in therange of 7.5 to 9.5 and including as essential constituents ferrous ionsin a concentration in the range of 12 to 16 grams per liter, nickel ionsin a concentration in the range of 3 to 10 grams per liter, molybdenum(VI) in a concentration in the range of .1 to 1 gram per liter, ammoniumions in a concentration in the range of 12 to 34 grams per liter, and acomplexing agent capable of forming soluble ferrous, nickel, andmolybdenum (VI) complexes and 'being of sufficient concentration toprevent precipitation of ferrous, nickel, and molybdenum (VI) ions;subjecting an elongated electrically conductive carrier as a cathode toelectrolytic action in said bath for a time sufficient to effect thedeposition thereon of a ferromagnetic coating which has the property ofproviding a particularly oriented easy direction of magnetization whenstressed; and applying a torsional stress to said coating, relative to alongitudinal axis of said carrier, by an amount sufficient to establishin said coating an easy direction of magnetization which is oriented atan angle with respect to said longitudinal axis.

15. A process for fabricating magnetic computing devices comprising thesteps of: providing an aquous electrolytic bath containing ferrouschloride, nickel chloride, and sodium molybdate and including asessential constituents ferrous ions in a concentration in the range of12 to 16 grams per liter, nickel ions in a concentration in the range of3 to 10 grams per liter, molybdate ions in a concentration in the rangeof .3 to 2 grams per liter, and a complexing agent, said bath having apH in the range of 7.5 to 9.5; subjecting an elongated electricallyconductive carrier as a cathode to electrolytic action in said bath fora time sufficient to effect the deposition thereon of a ferromagneticcoating which has the property of providing a particularly oriented easydirection of magnetization when stressed; and applying a torsionalstress to said coating, relative to a longitudinal axis of said carrier,by an amount sufficient to establish in said coating an easy directionof magnetization which is oriented at an angle with respect to saidlongitudinal axis.

16. A process for fabricating magnetic computing devices comprising thesteps of: providing an aqueous electrolytic bath containing ferrouschloride, nickel chloride, and sodium molybdate and including asessential constituents ferrous ions in a concentration in the range of12 to 16 grams per liter, nickel ions in a concentration in the range of3 to 10 grams per liter, molybdate ions in a concentration in the rangeof .3 to 2 grams per liter, and a complexing agent consisting of citrateions in a concentration in the range of 88 to 113 grams per liter, saidbath having a pH in the range of 7.5 to 9.5; subjecting an elongatedelectrically conductive carrier as a cathode to electrolytic action insaid bath for a time sufficient to effect the deposition thereon of aferro magnetic coating which has the property of providing aparticularly oriented easy direction of magnetization when stressed; andapplying a torsional stress to said coating, relative to a longitudinalaxis of said carrier, by an amount sufiicient to establish in saidcoating an easy direction of magnetization which is oriented at an anglewith respect to said longitudinal axis.

17. A process for fabricating magnetic computing devices comprising thesteps of: providing an aqueous electrolytic bath including as essentialconstituents ferrous ions in a concentration in the range of 12 to 16grams per liter, nickel ions in a concentration in the range of 3 to 10grams per liter, molybdenum (VI) in a concentration in the range of .1to 1 gram per liter, ammonium ions in a concentration in the range of 12to 34 grams per liter, and a complexing agent consisting of citrate ionsin a concentration in the range of 88 to 113 grams per liter, said bathhaving a pH in the range of 7.5 to 9.5; subjecting an elongatedelectrically conductive carrier as a cathode to electrolytic action insaid bath for a time sufficient to effect the deposition thereon of aferromagnetic coating which has the property of providing a particularlyoriented easy direction of magnetization when stressed; and applying atorsional stress to said coating, relative to a longitudinal axis ofsaid carrier, by an amount sufficient to establish in said coating aneasy direction of magnetization which is oriented at an angle withrespect to said longitudinal axis.

18. A process for fabricating magnetic computing devices comprising thesteps of: providing an aqueous electrolytic bath containing ferrouschloride, nickel chloride,

and sodium molybdate and including as essential constituents ferrousions in a concentration in the range of 12 to 16 grams per liter, nickelions in a concentration in the range of 3 to grams per liter, molybdateions in a concentration in the range of .3 to 2 grams per liter,ammonium ions in a concentration in the range of 12 to 34 grams perliter, and a complexing agent consisting of citrate ions in aconcentration in the range of 88 to 113 grams per liter, said bathhaving a pH in the range of 7.5 to 9.5 by the addition of ammoniumhydroxide; subjecting an elongated electrically conductive carrier as acathode to electrolytic action in said bath for a time sufficient toeifect the deposition thereon of a ferromagnetic coating which has theproperty of providing a particularly oriented easy direction ofmagnetization when stressed; and applying a torsional stress to saidcoating, relative to a longitudinal axis of said carrier, by an amountsuificient to establish in said coating an easy direction ofmagnetization which is oriented at an angle with respect to saidlongitudinal axis.

19. A process for fabricating magnetic computing devices comprising thesteps of: providing an aqueous electrolytic bath having a pH in therange of 7.5 to 9.5 and including as essential constituents ferric ionsin a concentration in the range of .7 to 3 grams per liter, nickel ionsin a concentration in the range of 3 to 10 grams per lited, molybdenum(VI) in a concentration in the range of .l to 1 gram per liter, and acomplexing agent capable of forming soluble ferric, nickel, andmolybdenum (VI) complexes and being of suflicient concentration toprevent precipitation of ferric, nickel, and molybdenum (VI) ions;subjecting an elongated electrically conductive carrier as a cathode toelectrolytic action in said bath for a time sufficient to eifect thedeposition thereon of a ferromagnetic coating which has the property ofproviding a particularly oriented easy direction of magnetization whenstressed; and applying a torsional stress to said coating, relative to alongitudinal axis of said carrier, by an amount sufficient to establishin said coating an easy direction of magnetization which is oriented atan angle with respect to said longitudinal axis.

20. A process for fabricating magnetic computing devices comprising thesteps of: providing an aqueous electrolytic bath having a pH in therange of 7.5 to 9.5 and including as essential constituents ferric ionsin a concentration in the range of .7 to 3 grams per liter, nickel ionsin a concentration in the range of 3 to 10 grams per liter, molybdenum(VI) in a concentration in the range of .1 to 1 gram per liter, and acomplexing agent consisting of citrate ions in a concentration of 33 to104 grams per liter; subjecting an elongated electrically conductivecarrier as a cathode to electrolytic action in said bath for a timesufficient to effect the deposition thereon of a ferromagnetic coatingwhich has the property of providing a particularly oriented easydirection of magnetization when stressed; and applying a torsionalstress to said coating, relative to a longitudinal axis of said carrier,by an amount sufiicient to establish in said coating an easy directionof magnetization which is oriented at an angle with respect to saidlongitudinal axis.

21. A process for fabricating magnetic computing devices comprising thesteps of: providing an aqueous electrolytic bath having a pH in therange of 7.5 to 9.5 and including as essential constituents ferric ionsin a concentration in the range of .7 to 3 grams per liter, nickel ionsin a concentration in the range of 3 to 10 grams per liter, molybdenum(VI) in a concentration in the range of .1 to 1 gram per liter, ammoniumions in a concentration in the range of 8 to 25 grams per liter, and acomplexing agent capable of forming soluble ferric, nickel, andmolybdenum (VI) complexes and being of suflicient concentration toprevent precipitation of ferric, nickel, and molybdenum (VI) ions;subjecting an elongated electrically conductive carrier as a cathode toelectrolytic action in said bath for a time sufiicient to effect thedeposition thereon of a ferromagnetic coating which has the property ofproviding a particularly oriented easy direction of magnetization whenstressed; and applying a torsional stress to said coating, relative to alongitudinal axis of said carrier, by an amount suflicient to establishin said coating an easy direction of magnetization which is oriented atan angle with respect to said longitudinal axis.

22. A process for fabricating magnetic computing devices comprising thesteps of: providing an aqueous electrolytic bath containing ferricchloride, nickel chloride, and sodium molybdate and including asessential constituents ferric ions in a concentration in the range of .7to 3 grams per liter, nickel ions in a concentration in the range of 3to 10 grams per liter, molybdate ions in a concentration in the range of.3 to 2 grams per liter, and a complexing agent capable of formingsoluble ferric, nickel, and molybdate complexes and being of sufficientconcentration to prevent precipitation of said ferric, nickel, andmolybdate ions, said bath having a pH in the range of 7.5 to 9.5;subjecting an elongated electrically conductive carrier as a cathode toelectrolytic action in said bath for a time suflicient to effect thedeposition thereon of a ferromagnetic coating which has the property ofproviding a particularly oriented easy direction of magnetization whenstressed; and applying a torsional stress to said coating, relative to alongitudinal axis of said carrier, by an amount suflicient to establishin said coating an easy direction of magnetization which is oriented atan angle with respect to said longitudinal axis.

23. A process for fabricating magnetic computing devices comprising thesteps of: providing an aqueous electrolytic bath containing ferricchloride, nickel chloride, and sodium molybdate and including asessential constituents ferric ions in a concentration in the range of .7to 3 grams per liter, nickel ions in a concentration in the range of 3to 10 grams per liter, molybdate ions in a concentration in the range of.3 to 2 grams per liter, and a complexing agent consisting of citrateions in a concentration in the range of 33 to 104 grams per liter, saidbath having a pH in the range of 7.5 to 9.5; subjecting an elongatedelectrically conductive carrier as a cathode to electrolytic action insaid bath for a time sufiicient to effect the deposition thereon of aferro magnetic coating which has the property of providing aparticularly oriented easy direction of magnetization when stressed; andapplying a torsional stress to said coating, relative to a longitudinalaxis of said carrier, by an amount sufiicient to establish in saidcoating an easy direction of magnetization which is oriented at an anglewith respect to said longitudinal axis.

24. A process for fabricating magnetic computing devices comprising thesteps of: providing an aqueous electrolytic bath including as essentialconstituents ferric ions in a concentration in the range of .7 to 3grams per liter, nickel ions in a concentration in the range of 3 to 10grams per liter, molybdenum (VI) in a concentration in the range of .lto 1 gram per liter, ammonium ions in a concentration in the range of 8to 25 grams per liter, and a complexing agent consisting of citrate ionsin a concentration in the range of 33 to 104 grams per liter, said bathhaving a pH in the range of 7.5 to 9.5; subjecting an elongatedelectrically conductive carrier as a cathode to electrolytic action insaid bath for a time suificient to effect the deposition thereon of aferromagnetic coating which has the property of providing a particularlyoriented easy direction of magnetization when stressed; and applying atorsional stress to said coating, relative to a longitudinal axis ofsaid carrier, by an amount sufiicient to establish in said coating aneasy direction of magnetization which is oriented at an anglewithrespect to said longitudinal axis.

25. A process for fabricating magnetic computing devices comprising thesteps of providing an aqueous electrolytic bath containing ferricchloride, nickel chloride, and sodium molybdate and including asessential constituents ferric ions in a concentration in the range of .7t0 3 grams per liter, nickel ions in a concentration in the range of 3to 10 grams per liter, molybdate ions in a concentration in the range of.3 to 2 'grams per liter, ammonium ions in a concentration in the rangeof 8 to 25 grams per liter, and a complexing agent consisting of citrateions in a concentration in the range of 33 to 104 grams per liter, saidbath having a pH in the range of 7.5 to 9.5 by the addition of ammoniumhydroxide; subjecting an elongated electrically conductive carrier as acathode to electrolytic action in said bath for a time sufficient toefiect the deposition thereon of a ferromagnetic coating which has theproperty of providing a particularly oriented easy direction ofmagnetization when stressed; and applying a torsional stress to saidcoating, relative to a longitudinal axis of said car- 14 rier, by anamount sufficient to establish in said coating an easy direction ofmagnetization which is oriented at an angle with respect to saidlongitudinal axis.

References Cited in the file of this patent UNITED STATES PATENTS1,837,355 Burns et al. Dec. 22, 1931 2,507,400 Marinis May 9, 19502,599,178 Holt et al June 3, 1952 FOREIGN PATENTS 18,378 Australia Oct.22, 1929 OTHER REFERENCES Bobeck: Bell System Technical Journal,November 1957, vol. XXXVI, pp. 1319-1340.

11. A PROCESS FOR FABRICATING MAGNETIC COMPUTING DEVICES COMPRISING THESTEPS OF: PROVIDING AN AQUEOUS ELETROLYTIC BATH HAVING A PH IN THE RANGEOF 7.5 TO 9.5 AND INCLUDING AS ESSENTIAL CONSTITUENTS IRON IN ACONCENTRATION IN THE RANGE OF .7 TO 16 GRAMS PER LITER, NICKEL IONS IN ACONCENTRATION IN THE RANGE OF 3 TO 10 GRAMS PER LITER, MOLYBDENUM (VI)IN A CONCENTRATION IN THE RANGE OF .1 TO 1 GRAM PER LITER, AND ACOMPLEXING AGENT CAPABLE OF FORMING SOLUBLE IRON, NICKEL, AND MOLYBDENUMCOMPLEXES AND BEING OF SUFFICIENT CONCENTRATION TO PREVENT PRECIPITATIONOF IRON, NICKEL, AND MOLYBDENUM IONS; SUBJECTING AN ELONGATEDELECTRICALLY CONDUCTIVE CARRIER AS A CATHODE TO ELECTROLYTIC ACTION INSAID BATH FOR A TIME SUFFICIENT TO EFFECT THE DEPOSITION THEREON OF AFERROMAGNETIC COATING WHICH HAS THE PROPERTY OF PROVIDING A PARTICULARLYORIENTED EASY DIRECTION OF MAGNETIZATION WHEN STRESSED; AND APPLYING ATORSIONAL STRESS TO SAID COATING, RELATIVE TO A LONGITUDINAL AXIS OFSAID CARRIER, BY AN AMOUNT SUFFICIENT TO ESTABLISH IN SAID COATING ANEASY DIRECTION OF MAGNETIZATION WHICH IS ORIENTED AT AN ANGLEE WITHRESPECT TO SAID LONGITUDINAL AXIS.